Root dentine and endodontic instrumentation: cutting edge microscopic imaging

Abstract

Cutting of the dental hard tissues is an integral part of restorative dentistry. Cutting of the root dentine is also needed in preparation prior to endodontic treatment, with significant commercial investment for the development of flexible cutting instruments based around nickel titanium (NiTi) alloys. This paper describes the evolution of endodontic cutting instruments, both in materials used, e.g. the transition from stainless steel to NiTi, and the design of the actual instruments themselves and their method of activation-by hand or motor driven. We have been examining tooth-cutting interactions microscopically for over 25 years using a variety of microscopic techniques; in particular, video-rate confocal microscopy. This has given a unique insight into how many of the procedures that we take for granted are achieved in clinical practice, by showing microscopic video images of the cutting as it occurs within the tooth. This technology has now been extended to allow imaging of the endodontic instrument and the root canal wall for the first time. We are able to image dentine distortion and crack propagation during endodontic filing of the root canal space. We are also able to visualize the often claimed, but seldom seen action of contemporary endodontic instruments.

Real‐time dynamic torque values and axial forces during preparation of straight root canals using three different endodontic motors and hand preparation

“…). However, other findings have demonstrated dentine distortion during root canal preparation (Atmeh & Watson ) and significant detectable strains on root surfaces (Pilo et al . ).…”

“…). Nevertheless, Atmeh & Watson () reported dentine distortion and crack propagation by examining tooth‐cutting interactions using video‐rate confocal microscopy and each intracanal mechanical manipulation seems to cause root surface strain (Pilo et al . ).…”

Evaluation of the cutting ability of two reciprocating instruments (WaveOne Gold e W-file)

“…Over the past 30 years, files have undergone continuous evolution, from hand-held stainless steel instruments to innovative nickel-titanium (NiTi) files that are superior to stainless steel files. (Yoo & Cho, 2012;Atmeh & Watson, 2016). Reciprocal movements are somewhat more efficient compared to rotary instruments and offer some advantages, such as reducing cyclic fatigue, instrument torsion, and optimizing working time (Da Graça & Paiva, 2020).…”

Reorienting Goals in Endodontic Therapy: Pulp Revitalization, on the brink of a paradigm shift.

“…This necrotic tissue still lodged in the pulp chamber offers a favourable environment for bacterial proliferation, which leads to periapical infections and resorption of apical tooth structure (1). Absence of hydration provided by the pulp causes reduction in the resilience of the coronal portion of the dental hard tissue (2), and makes teeth brittle which ultimately manifests into chipping or fracture of the coronal tooth upon subjection to masticatory stresses. This is both an aesthetic and functional dilemma.…”